A coaxial-lead, glass-sealed semiconductor diode, commonly referred to as a "glass diode," has been a standard device for many years. Typically, such devices have not required a metallurgical bond between the metal contacts of the semiconductor chip and the surfaces of the metal plug leads in contact therewith, since the stresses generated when forming the glass-to-metal seal have been considered sufficient to provide reliable electrical continuity under the conditions encountered during normal use.
In certain environments, however, reliability problems have developed due to intermittent electrical discontinuities, i.e., intermittent separation of the chip contacts from the metallic plug leads. In order to solve this problem, various attempts to obtain reliable alloy bondings have been made. For example, diffusion bonding between the plugs and the semiconductor metallization has been tried and proven insufficient. Also, prior attempts have frequently resulted in excessive interaction of the device metallization with the silicon chip, thereby altering the device performance characteristics, and even leading to excessive stress concentrations resulting in a fracture of the silicon chip.
Accordingly, it is an object of the present invention to provide a glass diode assembly having improved reliability. A more specific object of the invention is to provide a glass diode assembly wherein improved metallurgical bonding is obtained to eliminate intermittent electrical discontinuities.